Sigma 18-50mm F2.8 EX DC lens introduction : The characteristics of digital SLR cameras were taken into consideration when designing the lens power layout. The new advanced Sigma 18-50mm F2.8 EX DC lens design corrects various aberrations. This lens provides the utmost correction against lateral chromatic aberration which is a serious problem for digital SLR cameras. This lens is coated to get the best colour balance whilst cutting down flare and ghost caused by reflections from the digital image sensor and lens. It has excellent correction for vignetting and superior peripheral brightness is ensured. A Special Low Dispersion (SLD) lens and two aspherical lens elements provide excellent correction for all types of aberrations.

Sigma 18-50mm lens - Design
The design produces a compact and lightweight, yet robust, construction with an overall length of 84.1mm (3.3in.) and maximum diameter of 74.1mm (2.9in.) and weight of 445g (15.6oz). This lens has a minimum focusing distance of 28cm (11in.). It is equipped with inner focusing system. The non-rotating front lens element makes the lens suitable for using its petal-type lens hood and circular polarizing filters. It is an ideal large aperture standard zoom lens for digital SLR cameras featuring APS-C size image sensor.

Sigma - EX lenses details
EX series, large aperture zoom lens designed specifically for use with digital SLR cameras. Some of the EX details are: EX lens series denotes excellence of engineering and new technology, Compact and lightweight zoom despite large F2.8 aperture, Excellent correction for various types of aberration provided by one SLD (Special Low Dispersion) glass element and two aspherical lenses and Super Multi Layer (SML) coating reduces flare and ghosting from which digital cameras tend to suffer.